Protective means for the rapper drive shaft of an electrostatic precipitator



March 16, 1965 s. GUSTAFSSON 3,173,773

PROTECTIVE MEANS F QR THE RAPPER DRIVE SHAFT OF AN ELECTROSTATIC PRECIPITATOR Filed July 10, 1962 mvzu'ronz 5T IG G U5 TAFSSON ATT YS.

United States Patent 3 173 7 73 rnorncrrvn MnANs i on ran narrnn nnrvn SHAFT AN ELECTROSTATIC rnncrrrraron Stig Gustafsson, Ionlroping, dweden, assignor to Aktiebolaget Svensha Flaktfabrilren, Stockholm, Sweden Filed duly 10, 1962, Ser. No. 20%,784 Claims priority, appiication Sweden, Italy 12, 1951, 7,226/61 1 fillaim. (Ci. 55-112) The present invention relates to protective means for the rapper shaft or" an electrostatic precipitator, particularly to protective means having a shaft entry casing fitted onto a wall of the main enclosing casing of the precipitator around the insulating drive coupling portion of the shaft and which is electrically insulated from the shaft.

In order to maintain the insulating function of the insulating drive coupling portion of the rapper drive shaft it is important that dust leakage outwardly through the shaft opening into the main 'precipitator casing be prevented or, at least, prevented from collecting on the insulating drive coupling. It is already known that in order to avoid this risk, the shaft insulating coupling can be enclosed in a separate ante-chamber or entry casing equipped with a screw conveyor or scraper conveyor connected to the driving means and which carries away the dust precipitated in the chamber. See applicants Patent No. 2,864,- 459. As this conveyor must be arranged at a sutiicient distance from the inuslating coupling to eliminate the risk of fiashover, only part of the dust can be disposed of in this way, and there is still a risk that the insulating coupling will become covered with a conducting layer of dust.

The invention, which is designed to completely eliminate the said disadvantage and in a simple and reliable Way keep the said insulating coupling and adjacent parts of the shafts completely free from precipitated dust, is characterized in that the insulating coupling is enclosed in a separate chamber connected to the precipitator casing and also connected to a unit for supplying scavenging air under pressure, and in that a spaced tubular sleeve is arranged in the entry opening around the drive shaft and projects into the precipitator for discharging the said scavenging air into the main precipitator casing.

Scavenging air is delivered either tangentially at the end of the chamber remote from the precipitator, with the object of producing a rotary motion of the air towards the outlet; or, according to an alternative embodiment of the invention, scavenging air can be admitted radially through the outer wall of the shaft-enclosing easing into an annular space and then through a perforated cylinder arranged coaxially in the casing around the shaft.

The invention will now be described in more detail with reference to the accompanying drawing, which shows an advantageous embodiment of the device according to the invention.

In the drawing, 1 designates the casing of an electrostatic precipitator, which is equipped in a known way wit. a number of emitting and collecting electrodes, not shown in the drawing, and an equipment for rapping the electrodes clean. The last-mentioned equipment includes a rapping mechanism consisting of a number of rappers or hammers 2, attached to a horizontal shaft 3, arranged transversely in the precipitator. This rapping mechanism shaft is connected by means of an insulating coupling 4 to a separately mounted shaft 5, which is turned by means of a chain drive 6 from a motor 7. According to the invention, the insulating coupling 4 is enclosed in a chamber or casing 8, which is connected to the inside of the precipitator by means of a tubular sleeve 9. In the embodiment shown, a perforated cylinder 10 is mounted within the outer casing 8, and, together with the outer casing Wall, forms an annular space 1 for scavenging air which is delivered through an inlet 12 connected to any suitable means for supplying air under pressure. Instead of blowin the air radially into the chamber through the perforated cylinder in this Way, it can be given a rotary motion by arranging the supply tangentially at the chamber end remote from the precipitator, and the device can be varied in various Ways within the scope of the invention. Because of the positive pressure created by the supplied scavenging air in chamber 8 dust particles will largely be prevented from leaking from the main precipitator casing into the ante-chamber or entry casing 8 around the shaft opening; and dust that nevertheless does enter the casing 0 is prevented by the scavenging air from being deposited on the insulating coupling 4 or from being collected in the entry casing and so being carried by the air back into the precipitator.

lclairn:

Protective means for the rapper drive shaft of an electrostatic prccipitator, comprising in combination: a main precipitator casing having an oversize opening in a side for a rapper drive shaft; a rapper drive shaft extending through said main casing opening and, on the outside of said main casing, having an insulating drive coupling; a shaft entry casing secured to the side of the main casing around said opening and shaft and insulating shatt coupling; a perforated cylinder secured around the shaft and its insulating coupling and said opening and forming, with the walls of said entry casing and main casing, an annular distribution space around said shaft and its insulating coupling; means for supplying scavenging gas into said annular space to flow through the openings of said perforated cylinder into the space around said shaft and its insulating coupling; and a tubular sleeve secured in said opening around said shaft and extending into said main precipitator casing to define a discharge passage for scavenging gas around said shatt into said main precipitator casing.

References Cited by the Examiner UNITED STATES PATENTS 1,463,352 7/23 Weiskopf 55-112 X 2,198,618 4/40 Home -55-112 2,525,325 10/50 Viets 55-1 12 2,526,715 10/50 Viets 55-112 2,547,573 4/51 Gannone 55-112 2,655,264 10/53 Thorue 210- X 2,750,047 6/56 Hasbrouck 210-136 X 2,756,838 7/56 Roberts 55-101 2,842,938 7/58 Burton et al 55-112 X 2,864,459 12/58 Gustafsson 55-112 2,901,324 8/59 Howell 55-112 X 2,917,173 12/59 Rakowsky 209-211 X 3,090,746 5/63 Market, et al. 55-459 FOREIGN PATENTS 505,794 8/30 Germany. 565,152 10/32 Germany.

HARRY B. THORNTON, Primary Examiner.

ROBERT F. BURNETT, Examiner. 

